> On Mar 11, 2016, at 1:21 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> Hi-
>
> We observed some behavior at Connectathon between a
> v4.5-rc6 Linux client and a prototype Solaris 12 server
> when using NFSv4.1 on TCP. Test is xfstests generic/089.
>
> At an earlier point, the client has been granted a
> write delegation, denoted below by "state=w", and has
> closed the file.
>
> The sequence then observed on the wire is:
>
> C OPEN fh=A claim=DELEG_CUR_FH
> C LOCK fh=A zero stateid
> R OPEN NFS4_OK state=a
> R LOCK NFS4ERR_BAD_STATEID
> C TEST_STATEID state=a
> R TEST_STATEID NFS4_OK
>
> client reports "Lock reclaim failed!"
>
> C LOCK fh=A state=a
> R LOCK NFS4_OK
> C DELEGRETURN state=w
> R DELEGRETURN NFS4_OK
> C RENAME -> .nfsXXXXXXXXXX
> R RENAME NFS4_OK
>
> I've reproduced the problem here at home. Sometimes
> the LOCK operation is emitted just _before_ the
> OPEN.
>
> There are two processes involved. One is attempting
> to lock the file. The other is attempting to unlink
> the same file while it is still open.
>
> I'm not sure why the client is emitting the LOCK
> operation at all, since it still holds a write
> delegation. The "Lock reclaim failed!" message
> seems to reflect this confusion: It expects to find
> and recover lock state, but there hasn't been a
> successful LOCK on that file yet.
>
> After browsing the code, I don't see any serialization
> between taking a lock and returning a delegation on
> the same file, but my understanding in this area comes
> up short.
>
> Is there a preferred way to serialize these two
> activities (like, a particular mutex that should be
> held) ?
>
> Thanks for any guidance!
Following up.
Commit 24311f884 ('NFSv4: Recovery of recalled read
delegations is broken') introduced a
clear_bit(NFS_DELEGATED_STATE, &state->flags);
in nfs_open_delegation_recall().
That flag is cleared before the OPEN is emitted, leaving
a window where NFS_DELEGATED_STATE is clear, but there is
no valid open stateid with which to perform a LOCK.
Moving the clear_bit() into the NFS4_OK case in
nfs4_handle_delegation_recall_error() seems to eliminate
the race.
--
Chuck Lever
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